Objectives: To evaluate determinants of discordance between DAS28-ESR and DAS28-CRP and resulting impact on disease activity stratification in rheumatoid arthritis (RA)Methods: Paired DAS28-ESR and DAS28-CRP readings (n=31,074) were obtained from the British Society for Rheumatology Biologics Register for Rheumatoid Arthritis (BSRBR-RA). Factors influencing discordance between DAS28-ESR and DAS28-CRP were evaluated alongside the resulting effect on disease activity stratification. The impact of gender adjustment to the DAS28-CRP was evaluated. Results: DAS28-CRP scores were ~0.3 lower than DAS28-ESR overall, with greatest differences for women (-0.35) and patients over 50 years old (-0.34). Mean male DAS28-CRP scores were 0.15 less than corresponding DAS28-ESR scores. Discordance between DAS28-ESR and DAS28-CRP significantly impacted disease activity stratification at low disease activity (LDA) and remission thresholds (32.0% and 66.6% concordance respectively). Adjusting DAS28-CRP scores by gender significantly (p <0.001) improved agreement with the DAS28-ESR. Conclusion: Discordance between DAS28-ESR and DAS28-CRP is greatest for women and patients over 50 years of age, and influences disease activity stratification. The proposed gender adjusted DAS28-CRP improves inter-score agreement with DAS28-ESR, supporting more reliable disease activity stratification in treat-to-target approaches for RA.